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Sep 24 – 29, 2023
US/Eastern timezone

Shedding Light on Shadow Generalized Parton Distributions

Sep 25, 2023, 2:22 PM
18m
Meeting Room 3-4 (Durham Convention Center)

Meeting Room 3-4

Durham Convention Center

Talk 3D Structure of the Nucleon: GPDs and Form Factors 3D Structure of the Nucleon: GPDs and Form Factors

Speaker

Eric Moffat (Argonne National Lab)

Description

The feasibility of extracting generalized parton distributions (GPDs) from deeply-virtual Compton scattering (DVCS) data has recently been questioned because of the existence of an infinite set of so-called ``shadow GPDs'' (SGPDs). These SGPDs depend on the process and manifest as multiple solutions (at a fixed scale $Q^2$) to the inverse problem that needs to be solved to infer GPDs from DVCS data. SGPDs therefore pose a significant challenge for extracting GPDs from DVCS data. With this motivation we study the extent to which QCD evolution can provide constraints on SGPDs. This is possible because the known classes of SGPDs begin to contribute to observables after evolution, and can then be constrained (at the input scale $Q^2_0$) by data that has a finite $Q^2$ range. The impact that SGPDs could have on determining the total angular momentum, pressure and sheer force distributions, and tomography is also discussed. Our key finding is that scale evolution, coupled with data over a wide range of skewness $\xi$ and $Q^2$, can constrain the class of SGPDs that we studied and potentially make possible the extraction of GPDs from DVCS data over a limited range in the GPD variables.

Primary authors

Adam Freese Alexei Prokudin (JLab) Andreas Metz (Physics Department, Temple University, Philadelphia) Eric Moffat (Argonne National Lab) Ian Cloet (Argonne National Laboratory) Leonard Gamberg (Penn State Berks) Nobuo Sato (Jefferson Lab) Thomas Donohoe Wally Melnitchouk (Jefferson Lab)

Presentation materials